Performing operations on continuously moving strip material presents numerous problems. Usually such operations will be in the nature of stamping at spaced intervals, or blanking, or forming of such strip material. These operations conventionally are performed while the work piece material is stationary, using some kind of conventional press with upper and lower blades or dies, which simply close and open on the work piece.
In some cases operations have been performed on a moving strip by so-called “flying dies”.
In this type of operation the dies which shear, shape, or form the strip workpiece, are mounted on slides. The dies can slide forward along the path of the moving strip, close, and open, and then slide back again. Such flying dies are well known, and have been shown in patents for many years Rotary forming machines are also shown in more recent patents. In these machines the forming dies are mounted on pairs of upper and lower rotatable support rolls. Machines of this type were usually designed and built to perform specific continuous repetitive functions. They were not readily adaptable to either stamping, or blanking, or forming, depending on the operation desired. In addition such machines experienced other problems, such as in lubrication, wear, timing of operations, and sequencing of operations. One of many major applications for such machines is in the forming of sheet metal studs for use in construction. Opposite edges of such metal studs are conventionally roll formed to provide a channel shaped cross section, the so-called “C-section” stud. In a preferred form, such studs are formed with a series of openings blanked out from a sheet metal work piece. Strips of the work piece extend from edge to edge of the stud, between adjacent openings, and form struts across the stud. Edges of the work piece around the openings and strips, are formed at angles to provide flanges for increased strength. Such studs are more thermally efficient, and are also significantly lighter than conventional C-section studs.
In construction such C-section metal studs are used in place of wooden studs for framing walls. In this type of application the industry requires that the studs be fabricated in exact lengths. These lengths will vary depending on the design of the building.
Usually, in the case of these known rotary machines, the rotary operations were intended to be carried out as part of a complete roll forming line which will also have an uncoiler, in some cases a flattener, and, a series of conventional roll forming die stands, for roll forming edge flanges along the length of the stud. Such machinery was intended to be capable of continuous operation at hundreds of feet per minute.
This has not always been achieved due in part to shortcomings of the rotary forming apparatus which was then in use. In addition, such continuous production lines could not be repeatedly stopped and started again to accommodate the need for precise location of the openings in each stud. This causes a problem in the fabrication of studs for construction uses. The construction industry requires that the C-section studs be free of openings at each end of each stud. This is because such studs are conventionally used to frame walls. In this type of use, the studs extend vertically at spaced intervals. The upper and lower ends of the studs are secured in horizontal metal C-section channels in most case, similar to framing using wooden studs. To achieve this the studs must be free of openings at each end. This is difficult to achieve using any known machinery. It requires that the blanking of the openings and the forming of the edges be carried out in a precisely timed sequence. At each end of each stud work piece there must be a brief, momentary halt in the blanking and forming operations, so as to leave the two ends of each stud free of openings. However the actual movement of the strip work piece cannot stop, since as explained it is part of a larger facility operating on a continuous basis. Timing these spaces between openings, when the strip is moving continuously at high speeds, for example 2–300 feet per minute, or more in some cases, becomes a challenge to any machine operator.
Another consideration is the need to pass services through the studs. For this reason all openings in each stud must align with corresponding openings in adjacent studs.
A further and different factor is that stress requirements for studs may vary from one building, or application, to another. Interior walls or partitions will require a much lower strength stud than exterior, or bearing walls. This may require openings to be spaced further apart, or closer together, along the length of the stud, and may require wider or narrower struts between openings, to provide the specific strength required for the application. Obviously there will also be major changes in the thickness of the strip sheet metal. The entire production line of machines must be adaptable to all these variations, to achieve economical and efficient production.
A more obvious factor is that such rotary machines are costly. In the past it was sometimes necessary to have four rotary machine, arranged one after the other, along the movement path of the work piece, to first of all blank out openings, and then to form the edges of the work piece around the openings.
Four such machines were required in many cases because the shape of the openings in the workpiece was generally triangular, and adjacent openings were oriented in opposite directions and thus alternated along the length of the work piece. This required two sets of blanking dies and two sets of forming dies, and thus involved four rotary machines. In most cases such rotary machines had to be custom designed to suit a particular type of operation, and were not readily adaptable to be converted from one type of operation to another, depending on the needs of the customers of the fabricator.
In many cases a fifth rotary machine was required to cut the work piece to length. Such costs could be justified where production volumes were large. However in many cases where production could not be maintained on a continuous basis, or where orders required the production of a variety of different studs of different gauge and having different lengths and different specifications, such an investment could not be made. Clearly if rotary machines could be made, which could be adapted, by the owner, by relatively easy, in-plant adjustments, so that the machines could perform, at different times or in different locations, various different operations, such as stamping, blanking or forming, of strip material, and were readily adjustable to variations in specifications from one order to the next, then rotary machines could achieve a wider distribution.